Method of combining iron-base sintered alloys and copper-base sintered alloys

ABSTRACT

METHOD OF COMBINING IRON-BASE SINTERED ALLOYS AND COPPER-BASE SINTERED ALLOYS COMPRISES STEPS OF THINLY COATING MIXED POWDER OF COPPER AND NICKEL ONTO JOINT SURFACE OR IRON-BASE POWDER OR SINTERED MASS THEREOF, AND SUBJECTING THE COATING TO SINTERING PROCESS USING TEMPERATURE APPLOCABLE TO IRON-BASE POWDER. JOINT SURFACE OF COPPER-NICKEL IN THEN ABUTTED WITH FORMED MASS OD COPPERBASE POWDER AND AGAIN SUBJECTED TO SINTERING PROCESS USING TEMPERATURE APPLICABLE TO COPPER-BASE POWDER. IN TEGRAL PIECE IS THEREBY OBTAINED MOST SUITABLE FOR FABRICATING VALVE SEATS OF INTERNAL COMBUSTION ENGINES.

March 5, 1974 lTARu N||M| ETAL 3,795,511

METHOD OF COMBINING IRON-BASE SINTERED ALLOYS AND COPPER-BASE SINTEREDALLOYS Filed Oct. 22, 1971 Z7 1 W *HHIHW @2111 HI! l nun 2 United StatesPatent Japan Filed Oct. 22, 1971, Ser. No. 191,606 Claims priority,application Japan, Apr. 27, 1971, 46/331,680 Int. Cl. B21k J/24; B22f7/00 US. Cl. 75-208 1 Claim ABSTRACT OF THE DISCLOSURE Method ofcombining iron-base sintered alloys and copper-base sintered alloyscomprises steps of thinly coating mixed powder of copper and nickel ontojoint surface of iron-base powder or sintered mass thereof, andsubjecting the coating to sintering process using temperature applicableto iron-base powder. Joint surface of copper-nickel is then abutted withformed mass of copperbase powder and again subjected to sinteringprocess using temperature applicable to copper-base powder. Integralpiece is thereby obtained most suitable for fabricating valve seats ofinternal combustion engines.

BACKGROUND OF THE INVENTION The present invention relates to a method ofcombining iron-base sintered alloys and copper-base sintered alloys toproduce an integral and solid alloy. These alloys have excellentadaptability for use as valve seats in internal combustion engines.

When the head of an engine is made of cast iron and the valve seat isentirely made of a copper-base alloy, the copper-base material yieldsduring use due to the difference in the coefficient of thermal expansionbetween the two materials. Also, the valve seat tends to move away fromthe engine head when the engine is cooled. This problem may be solved byapplying copper-base sintered material to the part of the valve seatthat engages the face of the valve. Copper-base sintered material is ahighly suitable valve seat material. The remaining portion of the valveseat is fabricated of ironbase sintered material which has a high heatresistance and coefiicient of thermal expansion very close to that ofcast iron.

The above selected materials fully satisfy the requirements necessaryfor valve seat materials. However, when iron-base sintered material andcopper-base sintered mateiral are combined into an integral sinteredmass, the conventional practice is not easily applicable since the ironand copper materials have different melting points. Conventionalpractice, namely, utilization of changes in size appeared during thesintering process, hot forging, brazing with copper or copper-tincompositions, or combinations of the above are not suitable for thepurpose of combining iron-base and copper-base sintered alloys into anintegral mass.

SUMMARY OF THE INVENTION Accordingly, it is an object of the presentinvention to provide a method of combining iron-base and copperbasesintered alloys into a unitary alloy useful for the fabrication ofcomponents subjected to high temperature.

In accordance with the present invention a method is provided forcombining iron-base sintered alloys and copper-base sintered alloyswherein a mixed powder of copper and nickel is thinly coated onto thejoint surface of a formed mass of iron-base powder or the sintered massthereof. The coating is subjected to a sintering process utilizing thetemperature applicable to iron-base powder. The joint surface ofcopper-nickel is then abutted with a formed mass of copper-base powderand again subjected to a sintering process utilizing the temperatureapplicable to copper-base powder. A unitary composite material isthereby obtained, the material being most suitable for fabricating valveseats as used in internal combustion engines.

BRIEF DESCRIPTION OF THE DRAWING Novel features and advantages of thepresent invention in addition to those mentioned above will becomeapparent to those skilled in the art from a reading of the followingdetailed description in conjunction with the accompanying drawingwherein:

'FIG. 1 is a top plan view of a valve seat fabricated of materialprocessed in accordance with the present invention;

FIGS. 2 and 3 are cross sectional views of the valve seat of FIG. 1illustrating the procedure of the present invention for combiningdifferent alloys into a unitary composite alloy materials; and

FIG. 4 is a fragmental sectional view of the valve seat of FIGS. 1-3 inan internal combustion engine.

DETAILED DESCRIPTION OF THE INVENTION Referring in more particularity tothe drawings, the individual figures illustrate an annulus ofcopper-base material 1 associated with an annulus of iron-base material2. The interface between the annuli 1 and 2 comprises joint material 3.The copper-base 1, iron-base 2 and joint 3 material are formed into asintered mass 5 in the shape of a valve seat. As shown best in FIG. 4,the valve seat or sintered mass 5 cooperates with a head 4 of aninternal combustion engine.

According to the method of the present invention, ironbase sinteredmaterial and copper-base sintered material are combined together into anintensified unitary sintered material. The material thus combined isparticularly adaptable for fabricating those parts and components ofmachines for which anti-friction qualities and wear resistance areindispensable, such as valve seats for automobile engines.

As previously explained above, copper and nickel mixed powder isselected as the joint material 3. This mixture is composed ofelectrolytic copper powder of under mesh and carbonyl nickel powderhaving a particle size of about 414.. An iron-base formed mass orsintered mass thereof is thinly coated with a uniform layer of the jointmaterial 3. Alternatively, the copper-nickel powder mixture may beuniformly coated onto an iron-base mixed powder after which the materialis sintered at a temperature agreeable to iron-base sintered material.By this heat treating copper melts and permeates into iron-base sinteredmaterial, but by the existence of nickel, copper remains near thecombined surface, and nickel rich material remained on the surfacethereof. On the other hand, the surface of remained nickel (includescopper) becomes a rugged or rough. The sintered mass is then placed in amold and copper-base powder is filled in on top of it. Pressing thecopper-base mixed powder causes entangling engagement between the powderand the rugged or rough surface of the iron-base sintered material whichis rich with nickel. After this mass is sintered, nickel diffuses intothe copperbase material to provide a very intense joint surface andexcellent bond.

Concerning other joint materials, in the case of a 100% nickel thediffusion of nickel into the iron-base material is insufficient and theresultant surface after the first sintering process is lacking inruggedness or roughness.

As a result, when the copper-base mixed powder is formed on the nickeljoint material the resultant joint or bond is most unsatisfactory sincethe copper-base material lacks entangling engagement with the nickeljoint material. Also, joint materials of 100% copper or substanceshaving a melting point less than copper, for example coppertin alloys,are equally unsatisfactory since each of these joint materials diffusesin an excessive amount into the iron-base material. Additionally, whenusing such joint materials, very little remains on the surface after thefirst sintering process which is carried out at a temperature agreeableto the iron-base material. In the event some of the joint materialremains, the surface thereof after sintering is quite smooth and almostthe equivalent of the 100% nickel joint material. Moreover, sincecoppertin alloys have melting points close to the copper-base mixedpowder the sintering conditions are difiicult to select and maintain.

As is clear from the above, copper-nickel mixed powder should beutilized as the joint material in the present invention. Theadvantageous result of the present invention is obtained byappropriately choosing the mixing ratio of copper and nickel by takinginto consideration the constituents of the iron-base and copper-basematerials to be combined. The required joint strength is also important.

A preferred embodiment of the present invention is described below withreference to the present drawing.

EXAMPLE Mixed powder composed of 96% iron, 3% moly'bdenum and 1%graphite was filled into a metal mold. A mixed powder of 50% copper and50% nickel was then thinly and uniformly applied to the annulus 2, andthen formed under a pressure of 6 t./cn1. into an annulus 2 and 3, asbest illustrated in FIG. 2, which may also be sintered under thesintering conditions agreeable to the iron-base material as specifiedhereinafter. The thickness of the uniform layer was 0.5 to 1.0 mm. Themixed joint material powder 3 of 50% copper and 50% nickel was alsocoated onto a powder of 96% iron, 3% molybdenum and 1% carbon. Thelatter iron-base powder was formed in a metal mold under a pressure of 6t./cm. Each of the above masses was then sintered at a temperature of1150 to 1180 C. for 60 minutes in an ammonia cracked gas which met thesintering conditions for the iron-base material. Each sintered mass thusobtained was put into a metal mold and covered with a copper-base mixedpowder composed of 80% copper, 8% tin and 12% chromium. After pressingthe copper-base material under a pressure of 6 t/cm. the copper-basematerial had a shape similar to the annulus 1 shown in the drawing.Next, the material was sintered at a temperature of 900 to 950 C. forminutes in a nitrogen gas under conditions agreeable to the copper-basematerial. The twice sintered mass was again pressed under 6 t./cm. toprovide an accurately sized unitary composite material 5 composed of anannulus 2 of iron-base sintered material 1, an annulus 1 of copper-basesintered material 1 and a joint material layer 3, as shown best in FIG.3.

For the purpose of evaluation, the sintered mass 5 was inserted into thecast iron head 4 of an internal combustion engine (see FIG. 4). Thecopper-base material of the mass 5 engaged the face of the valve. Theinternal combustion engine was run at 5,200 r.p.m. for two hours under afull load after which it was cooled. This cycle was repeated and theiron-copper sintered material of the present invention was perfect evenafter 50 cycles. A copper-base sintered material of copper alloy (fusionmaterial) fell away from the cast iron engine head after several cycles.

What is claimed is:

1. A method of combining an iron-base sintered alloy and a copper-basesintered alloy comprising coating a mixed copper and nickel powder as abonding agent onto the joint surface of an iron-base mass, sintering thecopper and nickel powder at a temperature agreeable to the iron-basemass to thereby diffuse and permeate part of the copper and nickel ofthe bonding agent into the ironbase mass and thereby form a rough nickelrich surface on the joint surface of the iron-base mass, abutting aformed mass of copper-base powder at the surface of the copper-nickelcoating on the iron-base mass, and finally sintering the abutted massesat a temperature agreeable to the formed mass of copper-base powder tothereby diffuse part of the nickel of the copper and nickel coating ofthe iron-base mass into the copper-base mass whereby the masses areintensely combined together.

References Cited UNITED STATES PATENTS 2,753,859 7/1956 Bartlett 29-1822X 3,359,623 12/ 1967 Gwyn -208 R X 2,251,410 8/1941 Koehring et a1.75-208 R X BENJAMIN R. PADGE'I'I, Primary Examiner R. E. SCHAFER,Assistant Examiner US. Cl. X.R.

